The present invention relates to a focusing position adjusting mechanism for an interchangeable lens barrel of a type used primarily for single-lens reflex cameras.
A variety of focusing position adjusting mechanisms used in interchangeable lens barrels have been proposed, differing in design according to the type of lens drive systems. In a lens of a type in which focusing adjustment is carried out by adjusting the position of a focusing lens, the lens drive member is composed of a first member including a stopper member for regulating the infinity photographing position and the closest photographing position, and a second member having a helicoid and cam hole for driving the lens. The force of engagement between the first and second member is decreased to change the relative positions thereof in a circumferential direction to thereby adjust the focusing position. After adjustment, the force of engagement is decreased again, and the members are fixed.
When, in the above-described conventional mechanism, the members are fixed after adjustment, the members are deformed slightly, lowered especially in circularity, as a result of which it becomes difficult to smoothly move the focusing lens. In order to eliminate this difficulty, the two drive members must be increased in mechanical strength. Furthermore, in order to minimize the application of a radial load to the members, the structure of the mechanism must be such that the members are tightened thrustwise by a tightening force. Therefore, the conventional mechanism has little degree of freedom in design, and is a cause of the lens barrel being bulky.